The invention relates to the field of filters and in particular to the field of aquarium filters and filtering equipment.
In the art of home aquariums, it is known to use a filter system which continuously circulates the water through a filter medium and returns it to the aquarium. One type of aquarium filter system is of the external type and uses a small container mounted on the side of the aquarium which holds the filter medium. The water from the aquarium is drawn through filter material in the container by means of a water pump and then returned to the aquarium. The filter medium is usually in the form of particles of activated carbon or charcoal and a fluffy mass of synthetic resin fibers.
An external type of filter is shown in U.S. Pat. Nos. 3,513,978 to Newsteder and 3,525,435 to Conner.
The Newsteder device uses two separate compartments, each filled with a different filtering substance (i.e., fibrous filtering material and charcoal). The water flows through the fibrous material to the charcoal, through the charcoal and is then returned to the aquarium. In this type of filter, however, the compartment holding the charcoal must have very restricted openings to prevent the flow from washing away any charcoal dust or particles into the aquarium.
The Conner filter uses a perforated top with a depending filter bag that is filled with charcoal. The flow of the water is down through the top, out through the bag walls and returns to the tank. The Conner filter is wholly disposable. However, it allows waste particles to contaminate the charcoal as there is no filtration prior to its passage through the charcoal.
Another type of aquarium filter is the internal or underwater filter. A container is provided which includes a filter medium such as activated carbon or charcoal and a fluffy mass of synthetic resin fibers. An air lift is provided extending from the container and air is pumped down into the air lift from an external air pump. The air pumped into the air tube flows up through the air lift causing a suction to draw water into the container, pass it through the filter medium and up through the air lift along with the air bubbles.
In aquarium filtration, the filter medium provides various types of filtration activity. As the water flows through a porous wall, mechanical filtration of the water occurs with the walls acting as a sieve, retaining the solid contaminants. The activated carbon or charcoal provides a chemical filtration of the contaminated water. At the same time bacteria in the form of accumulated sludge and slime act upon the waste material dissolved in the water, thus providing biological filtration.
The most effective water purification is achieved when bacterial propagation is at a high point. However, at this point prior art filter cartridges usually become subject to clogging and must therefore be removed and replaced. The newly replaced filter cartridge is free of bacteria while the old filter cartridge with bacteria is discarded.
Because the entire filter cartridge is discarded, the filter itself loses the biological filtering effects of micro-organisms. These organisms are natural filters because their life functions convert many of the harmful toxic wastes into harmless nitrates. In existing filter cartridges the entire cartridge is sealed and is completely replaced when it becomes clogged. Any bacterial organisms which may have grown within the filter cartridge are therefore discarded with the cartridge itself. This creates a void in filtering ability until the organisms re-establish themselves in the replaced filter cartridge. Additionally, since the filter cartridge is entirely sealed, the amount of carbon particles or other type of filtering material in the cartridge cannot be individually adjusted by the aquarium user himself.